Technical Field
The present disclosure relates to a terahertz wave measuring device, a terahertz wave measuring method, and a terahertz wave measuring rig.
Related Art
Conventionally, in general spectroscopic measurements and imaging using terahertz waves, emitted terahertz waves are guided so as to be incident on a sample, with a light source and the sample disposed separately from each other.
Moreover, terahertz wave characteristics measuring methods have been proposed that employ finely engineered structures, for example, micro electro mechanical systems (MEMS) and μ-total analysis systems (μ-TAS) (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2012-185151). In such methods, terahertz waves are radiated onto a portion of a liquid solution that includes at least one type of substance subject to measurement and that has a thickness in the range of from 10 μm to 100 μm, such that the propagation direction is the thickness direction of the liquid solution. The spectroscopic characteristics of terahertz waves transmitted or reflected by that portion, or the intensity of terahertz waves of a particular frequency or particular wavelength, is measured.
A terahertz wave probe has also been proposed that includes a tube-shaped conductor having an opening in its leading end, that includes an emitting device for emitting electromagnetic waves from a position distanced from the opening at one out of a portion at the outside or a portion at the inside of the tube-shaped conductor, and that includes a detection device for detecting electromagnetic waves from a position distanced from the opening at the other portion (for example, see JP-A No. 2007-248316). This terahertz wave probe is configured such that detected electromagnetic waves respectively emitted and detected at the inside portion and the outside portion of the tube-shaped conductor, which has a size of the opening that is the wavelength of the electromagnetic waves or less, are coupled through the opening, and information about a specimen is acquired based on changes in the coupling of the electromagnetic waves through the opening when the specimen to be inspected is positioned facing the opening.
A near-field microscope has also been proposed including a laser device that emits a specific laser light, a light condensing lens that condenses the laser light to a specific light condensing point, and an electromagnetic wave emitting element that emits the electromagnetic waves in the vicinity of the light condensing point of the laser light and emits near-field light of the electromagnetic waves in the vicinity of the outer surface of the electromagnetic wave emitting element (for example, see JP-A No. 2009-036693). This near-field microscope further includes: a scanning mechanism that moves the sample or the laser light to make the near-field light approach the sample, and that converts the near-field light into propagating light using interaction between near-field light and sample; an electromagnetic wave detector that detects the propagating light reflected by the sample or scattered by the sample, and that acquires an image of the sample; and a half mirror that transmits laser light and that reflects electromagnetic waves toward the electromagnetic wave detector.
However, in the device described by JP-A No. 2012-185151, although the sample is loaded into a micro flow path and measurement of terahertz waves is performed for a minute region, it is, for example, difficult to measure terahertz waves for a minute region that requires spatial resolution exceeding the diffraction limit of the terahertz waves.
Moreover, in the device described by JP-A No. 2007-248316, it is necessary to include elements having complex structures in the construction of the light source and the probe, since the generated terahertz waves must be propagated by the probe that includes an opening no larger than the wavelength thereof.
Moreover, in the device described by JP-A No. 2009-036693, interaction between the near-field light and the sample is utilized, and a structure is required that uses a half mirror to reflect terahertz waves transmitted by the measurement sample or scattered by the measurement sample, and that detects the terahertz waves. In such a structure, the terahertz waves transmitted or reflected by the measurement sample, or scattered by the measurement sample, are detected after being transmitted through the terahertz wave generation element. However, in such cases, sometimes the terahertz waves pass through interfaces formed by each material due to reflection from the terahertz wave generation element or from the sample, or from the rear face of the sample, and are affected by absorption and reflection of the terahertz waves in the terahertz wave generation element, the sample, and in free space, leading to the need to perform complex calculation or data processing in order to accurately measure the characteristics of the measurement target.